Cardiorespiratory Fitness May Help in Protecting Against Depression Among Middle School Adolescents.

PURPOSE: Cross-sectional studies demonstrate a robust association between depression, physical activity, and cardiorespiratory fitness in adolescents, but longitudinal evidence that can better parse the direction of these effects is scarce and conflicting, and no such studies in adolescents have considered the importance of fitness (as opposed to physical activity per se) for preventing depression. Therefore, the present study sought to determine if cardiorespiratory fitness in the first year of middle school (sixth grade) would protect against developing depression a year later (seventh grade), even after controlling for other risk factors (i.e., preexisting depression levels and weight status).
METHODS: Participants (N = 437 with 54.9% female) were recruited from six different middle schools during their sixth-grade year and reassessed during the seventh grade. At each assessment, participants completed self-report measures of depression and fitness. Participants were also weighed and were asked to complete a shuttle-run at both points.
RESULTS: A cross-lagged panel model indicated that cardiorespiratory fitness in the sixth grade was associated with significantly less depression by the seventh grade in girls, even after controlling for preexisting depression and weight. The effect was in the same direction for boys, but was nonsignificant. In both cases, effects were modest to small.
CONCLUSIONS: Cardiorespiratory fitness had a small, but significant protective effect against developing depression in middle school girls, and may have a similar but smaller effect in boys. Promotion of cardiorespiratory fitness can be an important strategy for preventing depression in middle school adolescents, but needs to be coupled with interventions that more directly address symptom treatment.